Since 2011, IHI and NEDO have been jointly developing an ocean current turbine based on a unique concept. In order to verify the validity of the concept in the ocean current, Kuroshio, IHI and NEDO developed an ocean current generator for demonstration called Kairyu. It comprises a combination of three cylindrical floats called pods, having a total length of approximately 20 m, a width of approximately 20 m, and a turbine rotor diameter of approximately 11 m. The two turbine rotors, left and right, are rotated in opposite directions to each other to cancel rotary torques associated with the rotation of the turbine rotors, thereby stably maintaining its position under water. The turbine system is moored from the anchor installed on the sea bottom and is suspended at underwater in operation. The depth of the sea is around 100 m, and the turbine system is installed at 30-50 m below sea surface. It can be floated up to the sea surface for maintenance. The rated flow speed is 1.5 m/s (approximately 3 knots) and the rated output, i.e., generating capacity is approximately 100 kW (50 kW × 2 units).
Since the autumn of 2019, the oceanic current turbine system has been demonstrated. They developed a robust system by repairing and improving the demonstration devices to improve the durability of the demonstration system and the functions of onshore electrical equipment. Then they made efforts to for further improve the installation method and to assess the risks. The power generation fluctuation analysis and the Kuroshio hovering test will be carried out in the Kuroshio area to verify the power generation performance of the demonstration device. In addition, they will understand and verify the feasibility of the system by acquiring long-term sea state data and analysing the energy potential of oceanic currents. After the test, the demonstration device will be removed and disassembled. The inside and outside of the device will be investigated in detail to validate the construction and installation method, salt damage, biofouling countermeasures, remote monitoring system, etc. The purpose of 2021 is to show that the oceanic current energy generation system has sufficient economic efficiency (power generation cost 40 yen / kWh) for electric source of separated islands from 2030.
Located off Kuchinoshima and Nakanoshima of Toshima Village (Kagoshima Prefecture).
Kairyu was completed in July 2017, and in August 2017, IHI and NEDO conducted a demonstration experiment of the ocean current turbine located off the coast of Kuchinoshima Island, Kagoshima Prefecture and obtained data for commercialization. The demonstration experiment was conducted for seven days.
Prior to the demonstration experiment, they conducted a towing test in the Koshiki Straits off the coast of Noma Misaki Cape (Minamisatsuma City, Kagoshima Prefecture) with the objective of verifying the power-generating performance and underwater behavior of the ocean current turbine.
From 2018 to 2021, the oceanic current turbine system was demonstrated in the Kuroshio area.